1. Field of the Disclosure
The present disclosure relates to a flexible display device and a method of fabricating the same.
2. Discussion of the Prior Art
Recently, flexible display devices using organic light emitting diodes (OLEDs) have been widely developed.
In more detail, categories of OLEDs include a passive matrix type and an active matrix type according to a driving method.
Further, OLEDs may be categorized into a top emission type emitting light to a top surface, a bottom emission type emitting light to a substrate where a thin film transistor (TFT) is formed (e.g., to a bottom surface), and a dual emission type emitting light to both the top surface and the bottom surface.
The flexible display device generally includes a plastic substrate that is flexible and capable of being bent, an OLED element, and a passivation element that can endure bending.
Further, the flexible display device is designed to have a structure that can endure a specific bending radius according to the purpose of application and the field of application.
The bending radius is a radius of a bent surface when bending the flexible display device, and as the bending radius becomes smaller, the fields of application are various and the quality of the flexible display device increases. However, currently, the OLED element, the passivation element, and the materials thereof are limited, and thus reliability is reduced.
FIG. 1 is a cross-sectional view illustrating a flexible display device 10 according to the prior art.
Referring to FIG. 1, the flexible display device 10 includes a plastic substrate 11, a TFT and OLED element layer 12 formed on the plastic substrate 11, an encapsulation portion 13 protecting the TFT and OLED element layer 12, a circuit portion 14 applying a power signal and a data signal, which are supplied from an external portion, to the element layer 12, and a bottom film 15 protecting a bottom of the plastic substrate 11.
The circuit portion 14 includes an IC (integrated circuit) pad portion 14a of a COF (chip on film) type or a COG (chip on glass) type, which is formed on the plastic substrate 11, a resin layer 14b protecting the IC pad portion 14a, and a flexible printed circuit substrate 14c connected to the IC pad portion 14a. 
An upper peripheral area A1 and a circuit portion area A2 of the flexible display device 10 are generally in a non-luminous area, and the non-luminous areas A1 and A2 are bent to achieve a thin profile and miniaturization of the display device.
However, a bending stress is applied to the non-luminous area A1 and A2 in the bending process, and thus the circuit portion 14, the plastic substrate 11, or the OLED element layer 12 is destroyed.
Further, in the bending process, the bent area does not maintain a constant bending radius.